As for a rotating electric machine such as a turbine generator or the like, a gas of hydrogen or the like is used as a cooling medium, for cooling the interior of the machine. The cooling medium is sealed within the rotating electric machine by shaft-seal devices using sealing rings (for example, refer to Patent Documents 1 through 5). In that shaft-seal device, an oil passes through an oil feed pipe, and is supplied into a rear chamber of a sealing ring. The oil moves from that chamber toward inner circumferential side of the sealing ring. According to the structure described above, a rear-face temperature of the sealing ring is lowered in its portion close to an oil supply opening(s). Because the sealing ring cannot expand (nor deform), an oil film which covers the shaft becomes thinner in the portion close to the oil supply opening(s), so that temperatures of the oil film rise.
The rise in temperatures of the oil film gives rise to cause damage to the sealing ring. In order to curb variations of the temperatures, a sealing ring is manufactured with its inner diameter made larger in advance, resulting in excessively consuming the oil. The specifications of constituent components (pumps, filters, and the like) of the shaft-seal devices are designed to cope with this excessive amount of oil. In order to curb the amount of oil required to seal the gas, it is suitably adopted in that a plurality of oil-supply directions is made toward the sealing ring (for example, refer to Patent Document 1).